Process for producing spelter.



CHARLES H. FULTON, OF ST. LOUIS, MISSOURI, ASSIGNOR, BY MESNEASSIGNMENTS, TO

METALLURGICAL LABORATOBIE$, INCO PORATION OF ILLINOIS.

RPOBATED, 0F CI'ICAGO, ILLINOIS, A COR- manner;

No Drawing.

To all whom it may concern:

Be it known that I, CHARLES H. FUL'roN, a citizen of the United States,residing at St. Louis, Missouri, have invented a certain new and usefulImprovement in Processes for Producing Spelter, of which the followingis a full, clear, and exact description, such as will enable othersskilled in the art to which it appertains to make and use the same.

tion, or by electrolyzing pure zinc solutions,

or by distilling impure spelter or other material containing metalliczinc. When spelter is made by the latter method it is calledredistillation and is ordinarily carried out in a modified form of theordinary well known retort furnace.

One object of my present invention is to provide a novel process bywhich a good grade of spelter can be roducedat a low cost from bluepowder, zlnc dross and zinc ashes, impure spelter and other zinc-bearingmaterials containing zinc in the metallic form, obtained directly orindirectly by the treatment of zinc ores.

Another object is to provide a distilling process for the purposedescribed that can be accurately controlled. Other objects and desirablefeatures of my invention will be hereinafter pointed out.

Briefly described, my process consists in forming zinc-bearing materialcontaining zinc in the metallic form, into objects that will retaintheir substantially original form and volume when heated to a dist1llingtemperature, subjecting said objects to treatment in a distillingfurnace, so as to convert the metallic zinc in the material into vapor,and thereafter, condensing the zinc vapor into spelter in'a condenser.

The material from which the said objects are formed may consist of bluepowder, zinc dross and zinc ashes, impure spelter, or, in fact, anyzinc-bearing material containing zinc in the metallic form, producedeither directly or indirectly by the treatment of zinc ores. While it isimmaterial, so far as my broad idea is concerned, how sald ob- ISpecification of Letters Patent.

Application filed January 22, 1917. Serial No. 143,795.

Patented Dec. 4, 1911'? jects are formed, I prefer to form them bycombining finely-divided zinc-bearing materlal of any suitable kindcontaining zinc in the metallic form and a binding material in certainproportions, heating said mixture and forming it into solid objectsunder high pressure. The reducmg a ent that I prefer to use ispulverized co e and the binding material is either tar or hard coal tarpitch, as objects formed in the manner previously described from suchmaterials and zinc-bearing material containing zinc in the metallic formhave the same essential characteristics and desirable features as theore briquets described in my prior U. S. Patent N 0. 1,193,- 680, datedAugust 8, 1916, namely, they remain intact and preserve their form andvolume throughout the distilling operation to which they are subjected.The purpose of heating the mixture during the process with a reducingagent.

other suitable carbonaceous material may be used in place of hard coaltar pitch. Other reducing agents than coke may also be used, but it ispreferable to use coke, as it contains no volatile matter to be drivenoff preliminary to distillation; it gives rise to no gas during thedistilling operation, except the carbon monoxid formed by the union ofits carbon with the oxygen of the zinc oxid, which union constitutes thereducing reaction, and as its particles have assumed what may beconsidered their final form at the time the coke is incorporated in thebriquet, said particles will not break down during the distillingoperation, thus insuring the continued stability of the briquet duringand after the distilling operation.

The shape of the briquets is immaterial, but in practice I form themixture into briquets of spherical or cylindrical form in molds wheremthey are subjected to a pressure of between 500 lbs. and 1,000 lbs. persquare inch, so as to solidify the mixture and form it into a compactmass that will not swell and crack during the subsequent drying anddistilling operations. When a carbonaceous binding material is used, itis as i necessary to preheat the briquets prior to the distillingoperation, so as to drlve off the volatile matter in the bindin materialand convert said material into co e, thus elimit mating the possibilityof the zinc vapor being diluted by volatile hydrocarbons m thedistilling operation. This preheating of the briquets also tends to makethe brlquets better electrical conductors and is advantageous if thebriquets are electrically distilled, as hereinafter described. In thepreheating and dryin operation just referred to it is desirable t at thebriquets be protected from the action of oxygen, so as to prevent thecoke in the outer surface of the briquets from oxidizing, and thuscausing the outside of the briquet to assume a loose and friablecondition, with resulting disintegration of the surface of the briquet.It is also necessary, when tar 'is used as the binder, to support thebriquets in some suitable manner during the preheating operation, so asto prevent them from breaking down or collapsing. The preheatingoperatlon may consist of a separate and distinct step or the preheatingand distillation of the briquets can be merged into practically oneoperation by arranging raw briquets in the distilling chamber, and thereheating them either by the stored heat in said chamber, or by any othermeans.

The proportions of the coke and the metallic zinc-bearing materialsshould be such that a suilicient mass of porous material will be left inthe briquet after the distilling operation to maintain substantially theoriginal volume of the briquet. The proportions of course will vary withdifferent metallic zinc-bearing materials, but as a general rule, theamount of coke used should be suflicient so that the weight of thebriquet, after distillation, will not be less than 40% to 50% of theweight of the briquet before distillation. The amount of bindingmaterial used also varies with the degree of fineness of the coke andthe metallic zinc-bearing material, but sufficient binding materialshould be used to cause the particles of coke and zinc-bearing ma terialto be completely surrounded by a film of binder which unites themtogether into a coherent mass. I have found that satisfactory briquetsare produced if the amount of binder is between 12% and 15% of theweight of the metallic zinc-bearing material, plus the weight of thecoke, when moderately fine coke such as will pass through a ten-meshscreen and metallic zinc-bearing material, such as will pass through aten-mesh screen, or finer, are used. It is essential that the metalliczinc-bearing material be in a relatively fine state of division at thetime it is mixed with the coke and binder. Blue powder, zinc ashes,etc., 65 are naturally so, and therefore, require no preliminarytreatment, but crude spelter has to be converted into granular form, forexample, by melting and granulating in water, before it is mixed withthe-binder and the coke. It is also desirable that the coke be finelyground, as such coke will produce a much stronger briquet thanmoderately fine or comparatively coarse coke.

After the briquets have been formed in the manner above described, theyare distilled in a distilling furnace, so as to cause the metalliczincin same to be driven ofl in the form of vapor, and thereafter, the zincvapor is admitted to a zinc condenser, wherein it is converted intospelter. The briquets can either be subjected to the usualzinc-distilling operation in the retorts of a spelter furnace, or theycan be electrically distilled. I prefer to electrically distil thebriquets in the manner described in my ending application Serial No.109,724, file July 17 1918, which briefly described, consists ininterosing one or more briquets as a continuous, xed resistor betweenelectrodes in a closed retort furnace and passing through them anelectric current of such strength as will cause the briquets to beheated to a distilling temperature. By varying the amount of currentpassed through the briquets the speed of distillation may be kept underperfect control and the rateof distillation be varied at will, thecurrent being preferably supplied to the furnace through a transformerso designed as to supply current of different voltage. If the current istoo great or too small at any given voltage, the voltage of thetransformer may be decreased or increased until the proper flow ofcurrent is obtained. The amount of current passed through the briquetsis preferably at first relatively small, so that the walls of the retortchamber of the furnace in which the briquets are arranged will be heatedrather gradually to about 700 C. or about 800 C. by radiation from thebriquets. The current he may then be rapidly increased and the briquetsraised to a distilling temperature.

It is immaterial what type of condenser .is used for converting the zincvapor into spelter, but I prefer to effect the recovery of the zinc in acondenser of the kind described in my pending application Serial No.141,177, filed January 8, 1917, which is so constructed that it can beeither heated or cooled, so as to maintain it within the propertemperature range.

By forming zinc-bearing materials containing zinc 1n the metallic forminto objects or briquets of the character previously described and thendistilling said briquets, I am able to recover a greater percentage ofthe zinc content of the material than is possible with any of theprocesses heretofore used in the manufacture of spelter practically freefrom the usual purities, 13o

impure metallic zine-bearing materials are used for the purpose ofredistillation, in that the control of the distillationgsas re gardstime and temperature, is veryclose. This control is of particularadvantage in the production of high grade spelter, since by distillingat the beginning at a relatively low temperature, most of the cadmiumcan be eliminated and some high cadmium spelter produced, after whichthe temperature may be adjusted to produce very pure spelter free fromcadmium, lead and iron, the lead not being appreciably distilled until arelatively hlgh temperature is reached, By proper manipulation of thecondenser, namely, draining the zinc therefrom, at the right time, thedifferent grades v,of spelter may be kept separate. 7

Having thus described my invention, what I claim, and desire to secureby Letters Patent, is: i

1. A process for manufacturing spelter, Y

which consists in forming zinc-bearing material containing zinc in themetallic form into objects that will retain substantially their originalform and volume when subjected to zinc distillation temperatures,heating said objects to convert the metallic zinc in the same intovapor, and thereafter condensing said zinc vapor into spelter.

2. A process for obtaining spelter, which consists in combiningfinely-divided, zinc-' bearing material containing zinc in the metallicform with a reducing agent and a binding material and forming saidmixture into objects that will retain their approximately original formand volume when subjected to zinc distillation temperatures,

heating said objects so as to drive ofi' the metallic zinc in the formof vapor, and thereafter converting said vapor into spelter.

3. A process for obtaining spelter, char-- acterized by combiningfinely-divided, zincbearing material containing zinc in the metallicform with coke and a carbonaceous binding material and forming saidmixture into briquets under pressure, heating said briquets sufficientlyto drive off the volatile matter in the carbonaceous binding materialand heating said briquets, and there after converting the Zinc vaporevolved in the distilling operation into spelter.

4. A-process for obtaining spelter, which consists in combiningzinc-bearing material containing zinc in the metallic form with areducing agent and a binding material of the charactermentioned and inapproximately the proportions specified, converting said mixture intobriquets that will not disintegrate when they are subjected to zincdistillation temperatures, and thereafter heating said briquets andcondensing the vapor evolved in the distilling operation into s elter.

5. process for obtaining spelter, which consists'in forming zinc-bearlngmaterial containing-zinc in the metallic form into briquets that aresubstantially free from hydrocarbon substances or compounds and whichwilretain their substantially original form and volume when subjected tozinc distillation temperatures, heating said briquets so as to driveofi' the metallic zinc in same in the form of vapor, and thereaftercondensing said vapor into spelter.

6. A process for obtaining spelter, which consists in formingzinc-bearing material containing zinc in the metallic form into briquetsthat will retain their substantially original form and volume whensubjected to zinc distillation temperatures, interposing one or more ofsaid briquets as a continuous resistor between the electrodes of anelectric furnace and passing a current of electricity through them toheat them to a distillation temperature, and thereafter condensing thezinc vapor evolved by the-heating of the briquets into spelter.

7. A process for forming briquets for use in the manufacture of spelter,characterized by combining zinc-bearing material containing. zinc in themetallic form with a reducing agent and a binding material in properproportions, forming said mixture into briquets under pressure, andthereafter heating said briquets so as to drive ofi' any hydrocarboncompounds in same which would tend to dilute the zinc vapors evolved inthe subsequent operation of heating the briquets.

8. A proces for manufacturing spelter, which consists in formingcompressed objects from finely divided spelter or zinc dross, coke and abinding material mixed in such proportions that said objects will retaintheir substantially original form and volume when subjected to zincdistillation temperatures, heating said objects to convert the metalliczinc in same into vapor, and thereafter condensing said vapor intospelter.

9. A briquet for use in the manufacture of spelter composed ofzinc-bearing material containing zinc in the metallic form, a reducingagent and a binding material combined into a compact mass that willretain its substantially original form and volume of spelter formed fromfinely-divided particles of zinc-bearing material containing zinc.

in the metallic form, a finely-divided reducing agent, and a substancethat unites the particles of said material and reducing agent into ,acoherent mass that Will retain substantially its original form andvolume when subjected to a zinc distilling temperature.

11. A briqnet for use in themanufacture of spelter, consisting of acompressed object composed of finely-divided, zinc-bearing maaocamaterial containing zinc in the metallic form, and a coke matrix, formedfrom a reducing agent and a carbonaceous binding substance in which theparticles of sai material are embedded.

12. A briquet for use in the manufacture of spelter," consisting of acompressed object composed of finely-divided, zinc-bearing materialcontaining zinc in the metallic form, coke, and the coked residue of acarbonaceous binder, such as tar or pitch.

CHARLES H. FULTON.

